Basic I/O Functions

3. Step-by-Step C/C++ --- C Programming - Basic IO Statements

Contents

• Structure of a C program

1. I/O Statements
2. Printf
3. Escape Characters
4. Using Variables in programs
5. Scanf

• More IO Statements

1. gets
2. puts
3. getch
4. putch
5. getche
6. getchar

As discussed, every program is a set of statements, and statement is an instruction to the computer, which is a collection of constants, variables, operators and statements.

Structure of a C program

<return type> main( arg-list )
{
     <declaration part>

     <Statement block>

     <Return Values >
}

We are going to start with Input / Output Statements as they play important roles in our further programs.

I/O Statements

Printf

This statement displays the given literal / prompt / identifiers on the screen with the given format.

Syntax:

printf(<"prompt/literal/format id/esc char. ">, id1,id2, .....);

E.g.:

printf("Hello");
printf("Student number : %d", sno);
printf("Student name : %s", name);
printf("3Subjects Marks : %d, %d, %d", m1, m2, m3);

1. Program to print a message:

/* 02_print.c */
#include <stdio.h>
int main( )
{
     printf("Hello");
     return 0;
}

Escape Characters

Common Escape Sequences

2. Program to print a message in a new line
- Compare with the last program.

/* 03_esc.c */
#include <stdio.h>
int main()
{
     printf("\nHello");
     return 0;
}

3. Program to display address of a person
- Multiple statements in main

/* 04_multi.c */
#include <stdio.h>
int main()
{
     printf("\nName of the Person");
     printf("\nStreet, Apartment//House No. ");
     printf("\nzip, City");
     printf("\nCountry");
     return 0;
}

Using Variables in programs

Basic Variable Types

4. Program to find the sum of two values
- Variables are introduced in this program

/* 05_var.c */
#include <stdio.h>
int main()
{
     int a , b , c;
     a = 5;
     b = 10;
     c = a + b;
     printf("%d", c);
     return 0;
}

5. Program to find the sum of two values with message
- Compare with the last program

#include <stdio.h>
int main()
{
     int a, b, c;
     a = 5;
     b = 10;
     c = a + b;
     printf("\nSum is %d", c);
     /* We have inserted extra text before printing the value*/
     return 0;
}

Scanf

Using this statement we can accept and values to variables during the execution of the program.

Syntax:

scanf(<format id/esc char">, id1,id2, .....);

Eg.

scanf("%d", &sno);
scanf("%s", name);
scanf("%d%d%d", &m1, &m2, &m3);

6. Program to find the sum of two value using scanf
- When you run the program it shows you the cursor and waits for your input, enter a numeric value and press "Return", do this twice and you will get the output.

/* 07_scanf.c */
#include <stdio.h>
int main()
{
     int a , b, c;      scanf("%d", &a);
     scanf("%d", &b);
     c = a + b;
     printf("\nSum is %d", c);
     return 0;
}

More Excercises:

7. Program to find the sum of two values with message display
- Messages are optional but introduces user-friendly interaction
- Compare with the last program

/* 08_sum.c */
#include <stdio.h>
int main()
{
     int a , b, c;      printf("Enter A value "); scanf("%d", &a);
     printf("Enter B value "); scanf("%d", &b);
     c = a + b;
     printf("\nSum is %d", c);
     return 0;
}

8. Program to find the result of ( a+ b )²
- Similar to sum of two values program but the formulae is different

/* 09_formula.c */
#include <stdio.h>
int main()
{
     int a, b, c;
     printf("Enter A value "); scanf("%d", &a);
     printf("Enter B value "); scanf("%d", &b);
     c = a * a + b * b + 2 * a * b;

     printf("Result is %d", c);
     return 0;
}

9. Program to find the annual salary of an employee
- input : eno, name, sal
- Process : Asal = sal * 12
- Output : Eno, name, sal, asal
- This program introduces the different types of variable

/* 10_emp.c */
#include <stdio.h>
int main()
{
     int eno;
     char name[10]; /* name with 10 characters width */
     float sal, asal; /* sal & asal as real values */
     printf("Enter Employee number "); scanf("%d", &eno);
     printf("Enter Employee name "); scanf("%s", name);
     printf("Enter Employee salary "); scanf("%f", &sal);

     asal = sal * 12;
     printf("\nEmployee number %d", eno);
     printf("\nEmployee name %s", name);
     printf("\nEmployee salary %f", sal);
     printf("\nAnnual Salary %f", asal);
     return 0;
}

10. Write a program to find the total and average marks of a student
- Input : Sno, name, sub1, sub2, sub3
- process : total = sub1 + sub2 + sub3; avg = total / 3
- output : sno, name, total, avg
- Similar to the above program just accept, process, and print the values

/* 11_stud.c */
#include <stdio.h>
int main()
{
     int sno, sub1, sub2, sub3, total;
     char name[10];
     float avg;

     clrscr(); /* clear the screen before its output */
     printf("Enter Student number "); scanf("%d", &sno);
     printf("Enter Student name "); scanf("%s", name);
     printf("Enter Subject1 marks "); scanf("%d", &sub1);
     printf("Enter Subject2 marks "); scanf("%d", &sub2);
     printf("Enter Subject3 marks "); scanf("%d", &sub3);

     total = sub1 + sub2 + sub3;
     avtg = total / 3;

     printf("\nStudent number %d", sno);
     printf("\nStudent name %s", name);
     printf("\nTotal marks %d", total);
     printf("\nAverage marks %f" , avg);
     return 0;
}

More IO Statements

Gets:

To accept a string from the key board. It accepts string value up to the carriage return.

Syntax:

gets( <id.> );

E.g.:

gets(name);
gets(street);

puts

It displays the given string value on the screen.

Syntax:

puts( <id.> / <“prompt”>);

E.g.:

puts(name);
puts(street);

getch - Read char without echo

getche - read char with echo

getchar - read char and accept carriage return

putch

It can print a character on the screen.

Syntax:

putch(<char>).

E.g.:

putch(‘a’);
putch(65);

getch

It accepts a character from console.

Syntax:

char = getch().

E.g.:

ch = getch();
option = getch();